Synchronizing joint

ABSTRACT

A joint for the angularly adjustable drive-connection of a cylinder block and a driveshaft of a hydrostatic bent axis piston unit. The joint has a shank which is rotatable about its longitudinal axis defining a joint axis, on both ends of the shank roller carriers project radially and basically perpendicular to the joint axis. On each roller carrier a roller is provided rotatable around a roller axis. The rollers are secured in axial direction against slipping-off of the roller carriers by means of an embossed area located axially outside of the roller on the respective distal end portion of the roller carrier.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims foreign priority benefits under 35 U.S.C. § 119to German Patent Application No. 102018218040.7 filed on Oct. 22, 2018,the content of which is hereby incorporated by reference in itsentirety.

TECHNICAL FIELD

The invention relates to a synchronizing joint for the angularlyadjustable drive connection of a driveshaft to a cylinder block of ahydrostatic bent axis axial piston unit. The invention in generalrelates to a universal joint for the angularly drive connection of twodriveshafts.

BACKGROUND

In the following the invention is descript by the help of a hydrostaticbent axis axial piston unit, exemplarily for a multitude of possibleuses for universal joints. A person skilled in the art will easilydetect that the inventive idea is applicable in general to all kind ofuniversal joints for the angularly drive connection of two driveshaftswhose driveshaft axes are not aligned, and wherein the distance of thedriveshaft ends facing each other changes with the variation of theangle between the driveshaft axes. In particular universal joints areused in hydrostatic propel units of the bent axis type of constructionin order to achieve a reliable, robust, smooth running and costeffective connection of the main rotating parts, i.e. the cylinder blockand the driveshaft, both being arranged in operation of the hydrostaticbent axis axial piston unit in an angularly position to each other, i.e.the so-called displacement angle which can be either fixed oradjustable, depending on the type of construction.

Hydrostatic bent axis axial piston units have a cylinder drum which ismounted so as to be rotatable about its longitudinal central axis andhas cylinder bores distributed over its periphery. In these cylinderbores working pistons are movable reciprocally. Hydrostatic bent axisaxial piston units of this type can be used as pumps or motors. In orderto adjust the displacement volume of the unit, the cylinder block can bepivoted about a pivot axis which runs transversely with respect to therotational axis of the cylinder block. As a result of which thelongitudinal central axis of the cylinder block forms an adjustableangle with the axis of the driveshaft. The working pistons arearticulately supported on a drive flange of the driveshaft at anadjustable angle. Another connection between the cylinder block anddriveshaft is produced by means of a synchronizing joint—a particularembodiment of a universal joint—ensuring the rotational synchronizationbetween the cylinder block and the driveshaft. On the ends of thesynchronizing joint at the driveshaft side and at the cylinder blockside in each case laterally projecting roller carriers are providedwhich each define an axis for rollers which are provided on the rollercarriers. The rotational axis of the rollers runs approximately at rightangles to the synchronizing joint axis. In general the rollers areprovided for ensuring a smooth displacement capability of the cylinderblock with respect to the driveshaft, i.e. a smooth articulationcapability, when the displacement angle between the driveshaft and thecylinder block is changed. When changing the displacement angle distancevariations between the cylinder block and the driveflange occur, inparticular for all points lying outside of the cylinder block centralaxis. These distance variations between the cylinder block and thedriveshaft/driveflange have to be compensated by pivot movements of thesynchronizing joint, wherein the synchronizing joint, is in its mostinserted position in the driveshaft or the cylinder block at adisplacement angle of cero degrees and is in its most outside positionat maximum displacement angle. This inside-out and vice versa pivotmovement have to be as smooth as possible to reduce the displacementforces.

The synchronizing joint also serves to ensure the torque transmissionbetween the shaft and the cylinder block in order to free the workingpistons from lateral forces as much as possible, which is valid inparticular when the hydrostatic bent axis axial piston unit is operatedin pump mode, i.e. when the driveshaft is driven externally. Even thoughhigh torques in all operation condition can occur at the synchronizingjoint in the event of, for instance, inhomogeneous loads or pressurepulses or in the event of hydraulic retardation of the cylinder drumwith respect to the driveshaft.

The synchronizing joint is therefore embodied as a joint with which therequired longitudinal compensation as well as transmission of hightorques can be provided in a reliable manner. For this purpose, thesynchronizing joint has a substantially cylindrical shank, wherein atthe two ends of which in each case one connecting pin is provided. Oneof which is basically aligned in the direction of the cylinder blockcentral axis and the other one in axial direction of the driveshaft. Bymeans of the connecting pins the synchronizing joint bears angularlycompensated under spring load at one side against the cylinder block andat the other side against the driveshaft. Said pressure springadditionally has the task of applying the necessary force for sealingoff the rotating cylinder drum with respect to the non-rotating valvesegment. This applies in particular to the unpressurized state, forexample when the motor is started up. Said spring forces must in anycase be transmitted by the synchronizing joint. On account of thekinematics during the pivoting of the cylinder drum, it is necessary forthe roller carriers to be designed such that the mobility of the rollerson the roller carriers is ensured. The angular compensation of thesynchronizing joint with respect to the cylinder block axis and thedriveshaft axis is generally achieved in that the connecting pinscomprise at that end facing the synchronizing joint a spherical surfacewhich abuts against a correspondent concave seat on the synchronizingjoint.

The torque transmitting capability of the synchronizing joint is ensuredby the roller carriers bearing slide rollers for ensuring the abovedescript pivot movement of the synchronizing joint when the displacementangle of the hydrostatic bent axis axial piston unit is changed. Otherstate of the art hydrostatic bent axis axial piston units use a cardanjoint which is a special universal joint not capable to compensatedistance variations, instead of the synchronizing joint according to theinvention. As a cardan joint bears the disadvantage of not being capableof compensating for distance changes, this have to be provided in adifferent manner, for instance, by the help of a splined shaft orsomehow else. It is obvious for a skilled person that using a splinedshaft for pivot movement does not offer an optimum result.

Hydrostatic bent axis axial piston units using a synchronizing joint ofthe described type are known, for example, from the company documentDanfoss-H1 Bent Axis Motors, Technical Information, pages 6 & 7, March2018. The assembly or disassembly of the synchronizing joint, however,is relatively complex because the multitude of components, in particularthe rollers and connecting pins, which are finally fixed when havingreached their designated position in the assembled hydrostatic bent axisaxial piston unit. Therefore, for assembly reasons, all the parts havebe provisionally fixed together before assembling, e.g. using auxiliarymeans for assembly. A conventional means is grease which temporarilyholds/adheres the parts in position and is washed away by surroundingoil when the hydrostatic bent axis axial piston unit is set inoperation. As a result of which the hydraulic fluid/oil and the filterrequired for cleaning the hydraulic fluid are contaminated. Further,grease is a dirt magnet bringing-in eventually dirt into the hydrostaticbent axis axial piston unit when assembling the unit or holding backwear particles which normally are flushed out of the unit. For a betterdissolving of the grease, light-type greases, like Vaseline, are usedhaving the disadvantage that their adhering properties are relativelylow, such that the rollers tent to drop-down during the assemblyprocess. This will cause an undesired breakdown in operation ofhydrostatic bent axis axial piston unit.

From DE 10 2007 051 369 B4 published also as US 2009/0111591 A1 anadditional securing elements are known, two of which are provided at thetwo ends of the cylindrical shank in order to prevent the rollers fromsliding off of the roller carriers by means of a Snap-On connection.

SUMMARY

The aim of the invention is to create an assembly-friendly universaljoint, in particular an synchronizing joint for a hydrostatic bent axisaxial piston unit which does not contaminate the hydraulic fluid,wherein the rollers are hold securely against drop-off of the rollercarriers during handling and assembling processes of the universaljoint, in particular the synchronizing joint to a hydrostatic bent axisaxial piston unit. It is also object of the invention to provide acosteffective, simple applicable and robust solution which works for alltype of bent axis axial piston units and which does not affectnegatively the lifespan of the hydrostatic bent axis axial piston unit.

According to the invention, the aim is achieved with a universal jointas disclosed herein and in particular in connection with a synchronizingjoint for an hydrostatic bent axis axial piston unit as known from DE 102007 051 369 B4 already mentioned before. The inventiveuniversal/synchronizing joint differs from the known synchronizingjoint, in that the rollers are secured in axial direction againstslipping-off of the roller carriers by means of an embossed area, which,with respect to the longitudinal synchronizing joint axis, islocated/applied axially outside of each roller on therespective/associated roller carrier. In the following the invention isdescribed exemplarily by the help of a synchronizing joint for ahydrostatic bent axis axial piston unit, however, as already statedabove, the invention is not limited to such synchronizing joints and canbe applied as well to any universal joint comprising at least one rollercarrier on which a roller can be mounted rotatable.

According to the exemplarily chosen embodiment the shank of asynchronizing joint in its assembled position between cylinder block andthe drive shaft is rotatable around a longitudinal axis which, atdisplacement angle not equal to cero, does not coincide neither with thecylinder block axis nor the drive shaft axis. In order to physicallyconnect the shank to both the cylinder block and to the drive shaftconnecting pins with spherical ends are used preferably. Accordingly,the shank, the cylinder block as well as the drive shaft show concavesupporting areas in which the connecting pins are supported pivotable,however capable of transmitting generally axial forces for maintaining aclosed contact between the cylinder block and the valve segment orpressure plate, respectively. This is particularly important at lowrevolution speeds or at standstill of the hydrostatic bent axis axialpiston unit in order to reduce losses due to leakage. This is particularpossible as no relative rotational speed difference between the driveshaft, the connecting pins, the shank and the cylinder block occursduring operation of the hydrostatic bent axis axial piston units.

For a person skilled in the art it is conceivable that by means of sucha synchronizing joint a variable adjustable hydrostatic bent axis axialpiston displacement unit is achieved, wherein the working pistons aregenerally free from circumferential forces, or in other words, thecircumferential forces on the working pistons is minimized by, forinstance in a preferred embodiment, a double tripod-like design of theshank, wherein each of the legs (roller carrier plus roller) is guidedin a corresponding groove (seat) in the cylinder block or in the driveshaft, respectively. In order that the synchronizing joint can bepivoted with respect to the drive shaft and the cylinder block, when thecylinder block tilt angle is changed, the tripod-like extensions of theshank are provided with rollers to facilitate this relative, curvedmotion of the shank relative to the cylinder block and the drive shaft.As there are no relative rotational speed differences between the axesof the shank, the driveshaft and the cylinder block, the rollers on theroller carriers do not require a sophisticated bearing, such that asliding contact bearing will suffice. However, when the displacementangle of the cylinder block with respect to the drive shaft is changed,the synchronizing joint motion should show very low forces alongraceways longitudinal formed on seats in the drive shaft and/or cylinderblock. With these inside-out movements of the synchronizing joint, i.e.the curved shank motion, distance compensation is provided too. As theshank is provided with at least one roller on a roller carrier on eachside of the shank each roller on its roller carrier is preferably to belubricated. This can be achieved by guiding “leakage” fluid from thevalve segment to the seats of the rollers in the cylinder block and/orthe driveshaft.

According to the invention the rollers are secured in axial directionagainst slipping-off of the roller carriers by means of an embossedarea. The embossed area is located with respect to the joint axis on therespective roller carriers and located axially outside of thecorresponding roller. In a preferred embodiment of the synchronizingjoint the shank shows three cylindrical extensions arrangedcircumferentially around each end portion of the shank. In thispreferred embodiment the shank comprises in total six rollers carrierswhich are cylindrically formed in order that each roller carrierreceives a roller thereon. The rollers are capable to rotate around thecylinder axis of the roller carriers and are secured againstslipping-off of the roller carriers by means of the before mentionedembossed area.

The embossed areas are located at the free distal end areas of theroller carriers and are applied to the roller carriers after placing theroller on the roller carrier. Once the roller is placed on the rollercarrier the embossed area is realized such that the roller is preventedfrom dropping-off of the roller carrier.

According to the invention the embossed area constitutes a locallylimited area in which the diameter of the in general cylindricallyformed roller carrier is increased such that the roller is preventedfrom slipping-off of the roller carrier. Hence, the embossed arealocally enhancing the outer diameter of the roller carrier should be inthis area at least equal than the internal diameter of the correspondingroller or slightly bigger. The embossed area should be in axialdirection big enough to ensure that the roller cannot slip-off of theroller carrier, however small enough that the roller can turn on theroller carrier, wherein the axial length of the roller carrier need notto be increased compared to roller carriers of already existingsynchronizing joints.

Thereby the embossed area can be performed with any suitable means knownfrom the state of the art. In preferred embodiments the embossed areacan be applied to the roller carrier for example by a welding point, awelding dash or a welding line, e.g., applied along the circumferentialdirection on the respective distal ends of the roller carriers or cansimply be a burr or a splint or an O-ring.

In a preferred embodiment of the invention the embossed area can be alaser welding point a laser welding dash or a laser welding line. Thisembossed area can be brought-up onto the roller carrier by means oflaser application, however, one can imagine also the addition ofmaterial by soldering, welding, sputtering, gluing and any othertechnology, which increases locally the diameter of the roller carriersat its distal ends. Preferably the embossed area is formed by laserapplication forming a laser point, a laser dash or a laser line, as thisdoes not introduce any additional material to the synchronizing jointduring the mounting step of the synchronizing joint and hence reducesthe risk of introducing dirt into the hydraulic unit. Further, by usinga laser application, assembling time is saved and the presence of e.g. alaser point or dash can be controlled easily by visual appearance on thesurface. A further advantage of laser application lies in the fact thatno high amounts of energy are introduced to the roller carriers suchthat heat deformations or mechanical deformations to the roller carriersare avoided. A further advantage lies in the fact that no additionalmaterial is added to the synchronizing joint, which also eliminates therisk from separating during use of the hydrostatic bent axis axialpiston unit.

By the inventive idea other imaginable solutions for in general securinga turnable ring on a shaft, like a snap ring or a stopper fixed in theouter end area of the roller carrier are covered by the invention, too.For all solutions imaginable by a person with skills in the relevant artit have to be fulfilled that after applying the embossed area onto theroller carrier to prevent slipping-off of the roller from the rollercarrier, the roller has to be still rotatable, and that the embossedarea on the roller carrier shows an axial diameter equal or bigger thanthe internal diameter of the roller. Needless to say that the outerdiameter of the embossed area should be smaller than the outer diameterof the roller in order that the roller can roll inside its correspondingraceway in the cylinder block or the drive shaft, respectively. Further,it is sufficient that the embossed area do not run along the wholecircumferential length of the roller carrier. Part of thecircumferential length, especially when a laser application is used, isenough for holding the roller on the roller carrier during the assemblyof the joint to the machine.

Another advantageous point using a laser application is given in that nomechanical processing—with its correspondent preparation for mechanicalprocessing—is necessary. Furthermore, laser application can be performedon nearly every material simply by adjusting the applied power. Thiseventually also allows for the use of plastic materials for the shank,however in most hydraulic bent axis axial piston units a shank made ofmetal is preferred due to the high moment to be transmitted as well asaxial and radial forces which are applied to the shank. Independentlywhich material is used for the shank the rollers itself can be made ofplastic material as the load on the same during operation of thehydraulic bent axis axial piston unit are lower. Here also the use of alaser for applying the embossed area on the roller carriers may bepreferred, as deformation energy for building the embossed area isintroduced to the roller carriers locally only.

Only at 0°-degree displacement angle the roller axis is perpendicularwith respect to cylinder block axis and also with respect to the driveshaft axis, hence the external circumferential surface of the rollersshow preferably a convex shape in order to provide at any displacementangle of the hydrostatic bent axis axial piston unit a sufficient bigabutment area. Preferably the roller carriers are formed integrally withthe shank showing an in general cylindrical circumferential surface onwhich the rollers showing internally also a circumferential cylindricalshape are mounted. Preferably there is a slight gap between the internalcylindrical surface of the rollers and the external cylindrical surfaceof the roller carriers in order that the rollers can turn on the rollercarriers. In a preferred embodiment the cylindrical roller carriers showin direction of the cylinder axis a throughhole which connects with alongitudinal bore along the shank axis in order to bring lubricationfluid nearby the gap between the rollers and the roller carrier. Thislubrication fluid is preferably taken from the central part of thecylinder block on the surface connecting with the valve plate and isguided through a longitudinal bore through the cylinder block to theconnecting pin connecting a cylinder block with the shank. From theshank longitudinal bore this lubrication fluid or leakage fluid can beguided further to the roller carriers beneath the cylinder block and theroller carriers beneath the drive shaft.

Further preferably this lubrication fluid or leakage fluid is guidedfurther by the second connecting pin connecting the shank with the driveshaft in order to lubricate the support of the synchronizing joint inthe drive shaft. As this is preferably configured preferably as anelastic support showing a pressure spring, which pressure spring iselastically prestressed in the assembled condition of the hydrostaticbent axis axial piston unit and transmits pressure forces, e.g., via aslider on the connecting pin which connects with the shank, the slidershould be lubricated for easy movement. This lubrication channel comingfrom the contact surface of the cylinder block with valve plate passingthrough the connection pins and the shank and onto the slider can beextended in a further preferred embodiment also to the external surfaceof the drive shaft in order to lubricate the drive shaft bearings.

As described above in general, by means of the inventive synchronizingjoint a simple, robust and economic solution for providing an easyassemble of the (pre-) mounted synchronizing joint to a hydrostatic bentaxis axial piston unit is provided. Wherein the rollers on the rollercarriers of the shank are secured such that dropping-off of the rollersis prevented especially when the synchronizing joint is handled in theassemble process of the hydrostatic bent axis axial piston unit. Withthe inventive synchronizing joint an automatic assembling of thesynchronizing joint is possible as the rollers are prevented fromslipping-off of the roller carriers.

A person skilled in the art will transfer easily all the above givenexplanation also to a basic universal joint comprising at least oneroller on a roller carrier. Such a basic universal joint can be used,for instance, by joining two not aligned driving shafts, wherein one endof one shaft is formed as the above descript shank showing the at leastone roller carrier with a roller mounted thereto and which is hold inplace by an embossed area according to the invention. Following this,the end of the other shaft comprises a corresponding seat for thereception of the roller hold in place by the inventive embossing areaapplied on the distal end of the at least one roller carrier. Hence, theinvention provides also for general universal joints a simple andreliable manner of (pre-) mounting the rollers on the roller carriers inorder to simplify the assembly process of two shafts which in operationneed not to be aligned to each other, as this for example occurs in thedriven or non-driven axles of vehicles having independent suspension.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is shown below by the help of preferred embodiments of theabove mention synchronizing joint in more details which are shown in theattached Figures for exemplary purposes only and do not limit the scopeof the invention, in particular not to the application of the inventiveidea to synchronizing joints only. Further embodiments and modificationof the embodiments and the inventive idea, which are within theknowledge of a person with skills in the relevant art are covered by theinvention also, likewise combinations thereof. The Figures show:

FIG. 1 shows a hydrostatic bent axis axial piston unit according to oneembodiment of the invention in a sectional cut;

FIG. 2 shows a synchronizing joint according to the invention in aperspective exploded view in the non-assembled state;

FIGS. 3 and 3A show a synchronizing joint in the assembled state in asectional cut.

FIG. 4 is an enlarged view of detail A as shown in FIG. 1 of anembodiment of shank 13 and connecting pin 14.

DETAILED DESCRIPTION

FIG. 1 illustrates a hydrostatic bent axis axial piston unit 1 accordingto the invention in the form of a hydraulic motor in a sectional view.The unit can fundamentally also be operated as a pump. As oneembodiment, the hydrostatic bent axis piston unit 1 is of the variableadjustable displacement type of construction. The hydrostatic unit 1 hasa cylinder block 6 which is mounted so as to be rotatable about itscylinder block axis 26 and has cylinder bores 7 distributed about itsperiphery, in which pistons 5 are movable. The cylinder block 6 ismounted in a housing 11 so as to be pivotable about a pivot axis whichruns transversely with respect to its cylinder block axis 26, so thatthe cylinder block axis 26 of the cylinder block 6 forms an adjustableangle with the driveshaft axis 23 of the driveshaft 3 which itself ismounted transversally fixed and rotatable free in driveshaft bearings 10mounted in the housing 11. The pistons 5 are articulately supported onthe drive flange 4 of the driveshaft 3 at a settable angle. Theadjustment of the displacement volume takes place by means of anadjusting device 9, by means of which a valve segment 8 which isattached to the cylinder block 6 can be pivoted. According to certainembodiments, the cylinder block 6 of the hydrostatic bent axis pistonunit 1 can be swivelled to positive and negative displacement angles bymeans of an adjustment unit 9.

The drive connection, i.e. the torque transmission between the cylinderblock 6 and the driveshaft 3 is produced by means of a synchronizingjoint 2 which is embodied exemplarily as a double tripod joint. Saidsynchronizing joint 2 has a substantially cylindrical shank 13 which ismounted at its ends in each case by means of rollers 17 in the driveflange 4 and in the cylinder block 6, and is biased against the driveflange 4 and the cylinder block 6 connecting pins 14 under springloading by a pressure spring 15. In the driveshaft 3 and in the cylinderblock 6 raceways 22 are formed for the rollers 17, which raceways 22 aredesigned such that the synchronizing joint 2 is displaceable in eachcase axially in the driveshaft 3 and axially in the cylinder block 6.For this purpose, the rollers 17 have a spherical outer shape. In thisway, length compensation can take place for different pivot angles. Thepressure spring 15 is installed in the driveshaft 3. The pressing forceof said pressure spring 15 is transmitted via the two connecting pins 14and the shank 13 of the synchronizing joint 2 to the cylinder block 6 inorder to maintain a close contact of the upper end of the cylinder block6 with the pressure plate 20 and the valve segment 8 even at lowrevolution speeds or even at standstill of the hydraulic unit 1. Thus,according to certain embodiments, a hydrostatic bent axis piston unit 1having a cylinder block 6 and a driveshaft 3 connected by synchronizingjoint 2, is usable as hydrostatic bent axis piston pump or hydrostaticbent axis piston motor.

As illustrated in the exploded view of FIG. 2 , the synchronizing joint2 which is embodied exemplarily as a double tripod joint, and iscomposed substantially of two three-arm stars and a cylindrical shank 13which connects the two three-arm stars to one another. For this purpose,the shank 13 which is aligned in the direction of the joint axis 12 hasat its two ends in each case three roller carriers 16 forming thethree-arm star. The roller carriers 16 in each case define a roller axis18, which is aligned in general perpendicular to the joint axis 12, forreceiving the rollers 17 by means of which the synchronizing joint 2 ismounted at the one side in the driveshaft flange 4 of the driveshaft 3and at the other side in the cylinder block 6. The synchronizing joint 2is supported physically on one side to the cylinder block 6 and on theother side to driveshaft 3 by means of in each case one connecting pin14 (not shown in FIG. 2 ) abutting each against a concave seat 24 formedat the end areas of the shank 13. The connecting pins 14, as shown inFIG. 1 , are hold against the synchronizing joint 2 under the force ofthe pressure spring 15 (also not shown in FIG. 2 ) which is providedconcentrically in the driveshaft 3. The roller carriers 16 are offsetwith respect to one another by in each case 120° and projectperpendicularly from the shank 13.

It is obvious for a person skilled in the art that the double tripoddepicts merely one possible embodiment for a synchronizing joint 2 andthat various other possibilities of one-arm, two-arm, four-arm or morearm stars at the synchronizing joint 2 is viable, wherein anon-symmetrical design also viable, i.e. different numbers of arms onboth sides of the shank 13. In order to prevent the rollers 17 fromsliding-off the roller carriers 16 embossed areas 19 will be realized oneach roller carrier 16 after the roller 17 is placed over the rollercarrier 16. As FIG. 2 show an exploded view of the inventivesynchronizing joint 2 and hence the rollers 17 are not placed already attheir final destination, the embossed areas 19 (see FIG. 3 ) are stillnot applied. For applying the embossed areas 19 the axial length of thecylindrical roller carriers 16 is slightly bigger than the axial lengthof the rollers 17 such that the embossed areas 19 can be realizedaxially outside of the rollers 17—seen in axial direction of the rollercarriers 16.

FIG. 3 shows the mounted—ready for assembling—state of the synchronizingjoint 2 in longitudinal section. Illustrated are the roller carriers 16which are formed integrally with shank 13 and to which the rollers 17are attached in a displaceable fashion. Here, the rollers 17 arerotatable about the roller axis 18. With reference number 19 theembossed areas are depicted. This illustration of the embossed areas 19is exaggerated and for illustration purposes only, in particular for theversion where the embossed area is brought-up by laser application ontothe distal end portion of the outer surface of the roller carriers 16,the embossed areas 19 would be very much smaller, just enough to preventthe rollers 17 from slipping-off. In this case the maximum radial heightof the embossed area 18—seen perpendicular to the roller axis—would be,for instance, in the range of 0.1 mm to some tenth of mm only. Justenough to hold the roller 17 on the roller carrier 16 until thesynchronizing joint 2 is assembled into the hydrostatic bent axis axialpiston unit 1. According to some embodiments, the embossed area 19 is awelding point, a welding dash or a welding line along thecircumferential direction of the roller carrier 16 or a burr. Further,according to some embodiments, the embossed area 19 is brought up bymeans of laser application, soldering, welding, sputtering, gluing orany other technology increasing locally the diameter of the rollercarrier 16.

It is therefore possible during assembly for the synchronizing joint 2to be handled as a modular unit without the risk that the rollers wouldslide-off of the roller carriers 16. The base body of the joint, i.e.the shank 13 with the roller carriers 16 can be produced as a singlecast part or a forged part, as illustrated in FIG. 3 . The embossedareas 19 on the roller carriers 16 as well as the roller 17 should besufficiently stable to withstand the temperatures which occur in thepower unit, and must be sufficient abrasion-resistant because anyabrasion debris caused by the curved movement of the synchronizing joint2 transmitted to the rollers 16 would pass directly into the system bymeans of the surrounding oil. The roller 17 can for example be producedfrom plastic material (see, e.g., FIG. 3A). Injection moulding could besuitable for the production process of the rollers 17. Metallicmaterials such as steel or bronze are likewise suitable and can becorrespondingly processed in a punching and bending process.

The shank 13 comprises at both end sides a conical recess in form of aconcave seat 24 in which, for instance, a spherical or conical head ofthe connecting pins 14 can abut. According to some embodiments of thehydrostatic bent axis piston unit 1, the radial bores in the driveshaft3 are capable to guide lubrication fluid from the connecting pins 14 toshaft bearings 10 rotatably supporting driveshaft 3 in a housing 11 ofthe hydrostatic bent axis piston unit 1. According to certainembodiments of the hydrostatic bent axis piston unit 1, the connectingpins 14 comprise through holes 31 capable to guide lubrication fluidfrom the cylinder block 6 to the longitudinal bore 27 in the shank 13and from the shank 13 to the driveshaft 3 and vice versa. Thelongitudinal bore 27 in shank 13 ensures a sufficient supply withlubricating oil for the connecting pins 14 and further on to the slider33 (see FIG. 1 ) which abuts against pressure spring 15. As best can beseen from FIG. 3 transversal bores 32 along the axial direction of theroller carriers 16, which are connected to the longitudinal bore 27 ofthe shank 13, provides for lubrication of the rolling movement of therollers 17 on the roller carriers 16. Further, according to certainembodiments, the synchronizing joint 2 includes radial bores 28 in theroller carriers 16 connect radial to the roller axis 18 orientedtransversal bores 32 in the roller carriers 16 such that lubricationfluid from the longitudinal bore 27 in the shank 13 is capable to beguided to the rollers 17. Radial bores (schematically shown in FIG. 1 asitem 25) in the driveshaft (3) are capable to guide lubrication fluidfrom the connecting pins (14) to shaft bearings (10) rotatablesupporting driveshaft (3) in a housing (11) of the hydrostatic bent axispiston unit (1).

In summary the invention provides for a simple universal/synchronizingjoint which due to its low number of parts is economic in itsmanufacturing and is as well robust during operation of, e.g., thehydrostatic bent axis axial piston unit or an axle of a vehicle withindependent suspension. The inventive synchronizing joint also enablesan automatic assembly of the inventive universal/synchronizing joint tothe hydrostatic bent axis axial piston unit or the vehicle axle, as therollers 17 are prevented from falling-down of the roller carriers 16 bymeans of embossed areas 19 brought up as stoppers for the rollers 17 atthe distal ends of the roller carriers 16. Furthermore, as grease for“gluing” the rollers 17 to the roller carriers 16 is not necessary anylonger, the hydraulic fluid in hydrostatic bent axis axial piston unitswill not be contaminated by grease and dirt wash-up from thesynchronizing joint 2.

While the present disclosure has been illustrated and described withrespect to a particular embodiment thereof, it should be appreciated bythose of ordinary skill in the art that various modifications to thisdisclosure may be made without departing from the spirit and scope ofthe present disclosure.

What is claimed is:
 1. A synchronizing joint for an angularly adjustabledrive-connection of a cylinder block and a driveshaft of a hydrostaticbent axis piston unit, wherein the synchronizing joint has a shank whichis rotatable about its longitudinal axis defining a joint axis, whereinon both ends of the shank roller carriers project radially and basicallyperpendicular to the joint axis, wherein on each roller carrier a rolleris provided rotatable around a roller axis, and wherein the rollers aresecured in axial direction against slipping-off of the roller carriersby means of an embossed area located axially outside of the roller onthe respective distal end portion of the roller carrier, wherein theembossed area includes material added to the distal end portion of theroller carrier, wherein bores in the roller carriers extend transverselyfrom the longitudinal bore in the shank, and wherein radial bores extendfrom the transversely extending bores in the roller carriers such thatlubrication fluid from the longitudinal bore in the shank is capable tobe guided to the rollers.
 2. The synchronizing joint according to claim1, wherein the embossed area is a welding point, a welding dash or awelding line along the circumferential direction of the roller carrieror a burr.
 3. The synchronizing joint according to claim 1, wherein theembossed area is brought up by means of soldering, welding, sputtering,gluing or any other technology increasing locally the diameter of theroller carrier.
 4. The synchronizing joint according to claim 1, whereinthe synchronizing joint is embodied at least on one end as a tripodjoint.
 5. The synchronizing joint according to claim 1, wherein at eachaxial end of the shank concave seats for receiving connecting pins areformed.
 6. The synchronizing joint according to claim 1, wherein therollers are made of plastic material.
 7. The synchronizing jointaccording to claim 1, wherein the external circumferential surface ofthe rollers shows a convex shape.
 8. The synchronizing joint accordingto claim 1, wherein the roller carriers are integrally formed with theshank.
 9. The synchronizing joint according to claim 1, wherein theshank comprises a longitudinal bore capable to guide lubrication fluidalong the joint axis.
 10. A hydrostatic bent axis piston unit having acylinder block and a driveshaft connected by synchronizing jointaccording to claim 1, usable as hydrostatic bent axis piston pump orhydrostatic bent axis piston motor.
 11. The hydrostatic bent axis pistonunit according to claim 10, wherein each end of the shank comprises aconcave seat for receiving connection pins, and wherein each end of theconnection pins shows a convex or spherical head for being capable tosupport the synchronizing joint in an angular position with respect tothe cylinder block axis and/or in angular position with respect to thedriveshaft axis.
 12. The hydrostatic bent axis piston unit according toclaim 10, wherein the connecting pins comprise through holes capable toguide lubrication fluid from the cylinder block to the longitudinal borein the shank and from the shank to the driveshaft and vice versa. 13.The hydrostatic bent axis piston unit according to claim 12, whereinradial bores in the driveshaft are capable to guide lubrication fluidfrom the connecting pins to shaft bearings rotatable supportingdriveshaft in a housing of the hydrostatic bent axis piston unit. 14.The hydrostatic bent axis piston unit according to claim 10, wherein thehydrostatic bent axis piston unit is of the variable adjustabledisplacement type of construction.
 15. The hydrostatic bent axis pistonunit according to claim 14, wherein the cylinder block of thehydrostatic bent axis piston unit can be swivelled to positive andnegative displacement angels by means of an adjustment unit.
 16. Auniversal joint for an angularly adjustable drive-connection of twodriveshafts, having a shank which is rotatable about its longitudinalaxis defining a joint axis, wherein on at least one end of the shank aroller carrier projects radially and basically perpendicular to thejoint axis, wherein on the at least one roller carrier a roller isprovided rotatable around a roller axis, and wherein the roller issecured in axial direction of the roller axis against slipping-off ofthe roller carrier by means of an embossed area located axially outsideof the roller on the distal end portion of the roller carrier, whereinthe roller carriers are integrally formed with the shank, wherein boresin the roller carriers extend transversely from the longitudinal bore inthe shank, and wherein radial bores extend from the transverselyextending bores in the roller carriers such that lubrication fluid fromthe longitudinal bore in the shank is capable to be guided to therollers.
 17. The universal joint according to claim 16, wherein theembossed area is a welding point, a welding dash, a welding line or aburr along the circumferential direction of the roller carrier.
 18. Theuniversal joint according to claim 16, wherein the embossed area isbrought up by means of laser application, soldering, welding,sputtering, gluing or any other technology increasing locally thediameter of the roller carrier.
 19. The universal joint according toclaim 16, wherein the universal joint is embodied at least on one end asa tripod joint.
 20. The universal joint according to claim 16, whereinat each axial end of the shank concave seats for receiving connectingpins are formed.
 21. The universal joint according to claim 16, whereinthe rollers are made of plastic material.
 22. The universal jointaccording to claim 16, wherein the external circumferential surface ofthe rollers shows a convex shape.
 23. The universal joint according toclaim 16, wherein the shank comprises a longitudinal bore capable toguide lubrication fluid along the joint axis.